The present invention relates to an excimer laser device and, in more detail, to a magnetic bearing for supporting a cross flow fan and a motor for driving the cross flow fan.
FIG. 9 is a partial sectional view of an excimer laser device according to a prior art, and the prior art will be explained below based on FIG. 9.
In FIG. 9, a laser gas which is a medium for oscillating laser light is sealed in the chamber 2 of the excimer laser device. A cross flow fan 1 provided with a blade section 3 having a plurality of blades and a rotating shaft 9 is disposed in a predetermined position in the chamber 2. The cross flow fan 1 circulates the laser gas by giving driving force to the rotating shaft 9 to rotate the blade section 3, thereby guiding the laser gas to a space between discharge electrodes (not illustrated). The laser gas is excited by applying a predetermined high voltage across the discharge electrodes, thus oscillating laser light.
The cross flow fan 1 is rotatably supported at both ends of the rotating shaft 9 thereof by non-contact magnetic bearings 12 and 12 respectively disposed in a bearing housing 7 and a motor housing 8. The magnetic bearings 12 and 12 include inner ring magnetic substances 10 and 10 which are annularly mounted on the outer peripheral face of the rotating shaft 9 and rotate integrally with the rotating shaft 9 and outer ring magnet coils 11 and 11 annularly surrounding the outer peripheries of the inner ring magnetic substances 10 and 10 with predetermined clearances between them respectively. Electric currents are sent to the outer ring magnet coils 11 and 11 by a current introducing means (not illustrated) to attract the inner ring magnetic substances 10 and 10, thereby rotatably supporting the rotating shaft 9 in a non-contact state.
The cross flow fan 1 is driven by a motor 49 disposed in the motor housing 8. The motor 49 includes a rotor 48 annularly mounted on the outer peripheral face of the rotating shaft 9 and a stator 47 annularly surrounding the outer periphery of the rotor 48 with a predetermined clearance between them. The stator 47 is composed of an iron core and a coil, and a rotating magnetic field is generated at the inner peripheral portion thereof by sending an electric current to the coil, thereby rotating the rotor 48 to drive the cross flow fan 1.
In the case, the inner ring magnetic substances 10 and 10, the outer ring magnet coils 11 and 11, and the rotor 48 are commonly composed of ferromagnetic silicon steel plates. When these silicon steel plates or the stator 47 touch the laser gas, they react with fluorine contained in the laser gas, which causes the materials thereof to corrode or causes an impure gas to generate to thereby contaminate the laser gas. Therefore, coatings having corrosion resistance to fluorine such as nickel plating and the like are applied on the surfaces of the silicon steel plates or the stator 47, thus preventing corrosion and generation of the impure gas.
The aforesaid prior art, however, has disadvantages described below.
Specifically, since the inner ring magnetic substances 10 and 10, the outer ring magnet coils 11 and 11, and the rotor 48 are composed of laminated silicon steel plates, the end faces thereof have projections and recesses. Even if coatings are applied on the end faces having such projections and recesses, the coatings sometimes peel off since adhesion of the coatings and the end faces is poor, and hence the silicon steel plates may touch the laser gas. Consequently, silicon and the like contained in the silicon steel plates sometimes react with fluorine, thus causing the silicon steel plates to corrode and causing the generation of an impure gas to thereby contaminate the laser gas.
Since the stator 47 is also composed of a coil, the surface thereof has large projections and recesses. Moreover, since an insulating material is applied on the surface of the coil, a coating sometimes peels off. Therefore, there is the possibility that the coil and the iron core react with fluorine to thereby corrode, or to thereby generate an impure gas, resulting in the contamination of the laser gas.
As described above, the conventional motor 49 and the magnetic bearing 12 are disposed in positions where they directly touch a laser gas having corrosiveness, and coatings having resistance to the laser gas are applied thereon. However, there is a disadvantage that the coatings of the conventional motor 49 and the magnetic bearing 12 are easy to peel off, thereby causing corrosion of the motor and the magnet bearing or contamination of the laser gas to shorten the life of the laser gas.
In view of the aforesaid disadvantages, an object of the present invention is to provide an excimer laser device provided with a magnetic bearing and a motor which neither corrode due to a laser gas nor contaminate the laser gas.
To attain the above object, a first configuration of an excimer laser device according to the present invention is characterized in that in an excimer laser device including
a cross flow fan disposed in a chamber for circulating a laser gas by rotating a blade section around a rotating shaft,
magnetic bearings having outer ring magnet coils mounted in the vicinity of both ends of the inner wall of the chamber and inner ring magnetic substances attached to the outer portions of both sides of the blade section of the outer peripheral face of the rotating shaft and facing the inner peripheral faces of the outer ring magnet coils with predetermined spaces between them respectively, for rotatably supporting the rotating shaft by magnetic force generated by the outer ring magnet coils and the inner ring magnetic substances, and
a motor having a stator mounted in the vicinity of an end of the inner wall of the chamber and generating a rotating magnetic field at a predetermined frequency which is variable and a rotor attached to the outer peripheral face of the rotating shaft and facing the inner peripheral face of the stator with a predetermined space between them, for rotating the rotor by the rotating magnetic field of the stator to directly and rotationally drive the cross flow fan,
the outer ring magnet coils, the inner ring magnetic substances, the rotor, and the stator are respectively housed in shielded spaces shielded from the laser gas.
Alternatively, the configuration is characterized in that the outer ring magnet coils, the inner ring magnetic substances, the rotor, and the stator are each formed by working out of a bulk material, and that coatings having corrosion resistance to the laser gas are applied on the formed surfaces.
According to the above configuration, the outer ring magnet coils, the inner ring magnetic substances, the rotor, and the stator are respectively housed in the shielded spaces shielded from the laser gas, or they are formed by working out of bulk materials and coatings having corrosion resistance to the laser gas are applied on the surfaces thereof. As a result, components which compose the magnetic bearings and the motor never touch the laser gas, whereby they neither corrode nor contaminate the laser gas. Accordingly, failures in the excimer laser device are reduced and the life of the laser gas can be lengthened.
A second configuration of an excimer laser device according to the present invention is characterized in that in an excimer laser device including
a cross flow fan disposed in a chamber for circulating a laser gas by rotating a blade section around a rotating shaft,
magnetic bearings having outer ring magnet coils mounted in the vicinity of both ends of the inner wall of the chamber and inner ring magnetic substances attached to the outer portions of both sides of the blade section of the outer peripheral face of the rotating shaft and facing the inner peripheral faces of the outer ring magnet coils with predetermined spaces between them respectively, for rotatably supporting the rotating shaft by magnetic force generated by the outer ring magnet coils and the inner ring magnetic substances, and
a motor having a stator mounted in the vicinity of an end of the inner wall of the chamber and generating a rotating magnetic field at a predetermined frequency which is variable and a rotor attached to the outer peripheral face of the rotating shaft and facing the inner peripheral face of the stator with a predetermined space between them, for rotating the rotor by the rotating magnetic field of the stator to directly and rotationally drive the cross flow fan,
the outer ring magnet coils, the inner ring magnetic substances, and the stator are respectively housed in shielded spaces shielded from the laser gas, and
the rotor is formed into a cage shape out of a conductive material, and a coating having corrosion resistance to the laser gas is applied on the formed surface.
Alternatively, in this configuration, the outer ring magnet coils, the inner ring magnetic substances, and the stator are each formed by working out of a bulk material, and coatings having corrosion resistance to the laser gas are applied on the formed surfaces.
According to the above configuration, the outer ring magnet coils, the inner ring magnetic substances, and the stator are shielded from the laser gas similarly to the first configuration, and the rotor is formed into a cage shape and a fluorine-resistant coating is applied on the surface thereof. Thus, the rotor does not need to be polarized, thereby saving time and labor for processing for polarization. Further, it no longer happens that the driving force of the motor weakens due to a decrease in magnetic force of the rotor, whereby constant driving force is always secured. Furthermore, the rotor has a cage shape, thereby reducing the weight and saving electric power for driving the motor.